Filter unit



Jan., 9, 195i R. s. FARR 2,537,2l7

FILTER UNIT Filed Sept. 27, 1946 2 Sheets-Sheet l R. S. FARR FILTER UNITJan. 9, l95l 2 Sheets-Sheet 2 Filed sept. 27, 1946 PTTUQNEV Patented`an. 9, 19.151

` FILTER UNIT Richard S. Farr, Los Angeles, Calif., assignor to FarrCompany, Los An tion of California geles, Calif., a corpora- ApplicationSeptember 27, 1946, Serial No. 699,943 24 Claims. (Cl. 18S-71) Thisinvention relates to a filter unit and it I is a general object of theinvention to provide a simple, practical and improved construction for afilter unit effective for filtering air.

' This application is filed as a continuation in part of my co-pendingapplication entitled Air Filter Panel filed March 9, 1943, Serial No.478,513, now abandoned. f

Features of my invention are applicable, generally, to filters. However,my invention is primarilyconcerned with what I may term metallic filtersor with filters involving filters made of wire screen, and it isparticularly useful and practical for handling air to 'separate dust orlike foreign particles therefrom. I will in describing my inventionrefer to it as a metal air filter, and-I will disclose aform of theinvention particularly suited for handling air yto separate dust or likeforeign particles therefrom. However, it is to be understood that I donot wish such specific references to be interpreted as a limitation orrestriction upon the broader principles that I teach. t

-It is a general object of this invention to provide a filter unitinvolving a filler or filter pad comprising a laminated structure formedof wire screening and reinforced against failure or distortion and alsoagainst shifting or. Working of the sheets of screening. Metal airfilters such as Iam concerned with are used extensively to filter airfor internal combustion engines and consequently they are in many casessubject to vibration, and in the event of engine backfire they aresubjected to excessive pressures or surges..

It will be understood that where a wire screen type air filter isemployed to catch dust, or the like, it is desirable that the filter orfilter parts be maintained in a compact, tight form and that they befree of vibration, as otherwise dust or particles that are trappedfaresimply dislodged.

. A further object of .thisinvention lis to provide an air lter of thecharacter referred to involving simple, inexpensive, and ,easilytappliedAstructural features which effect. desirable i-reinforcement andstifiening without materially 'adding either to weight or cost.f v l. yvIt is another object of this invention to provide anA air filter ofthetype in which;l the filterA pad or packA is formedof aplura'ity ofsheets or layers of screening and whichinvolvesa simple, effectiveretaining means thatnot only stiifens or reinforces the several sheetsbut bondsrthem together minimizing danger of vibration and providing apractical, durable,end efiective construction. f

A further object of this invention is to provide an air lter of theVcharacter referred to wherein air is channeled through the lter so thatthere is a substantially uniform unidirectional flow of air through thefilter at all parts.

Another object of the invention is to provide an air lter ofthecharacter referred to wherein there are plates that act to channel theair through the filter and also stiffening members which stiffen andbond the sheets of screening together, which plates and stiffeningmembers cooperate to reinforce or stabilize each other and to acttogether in reinforcing the entire unit,

The various objects and features of my invention will be fullyunderstood from the following detailed description of typical preferredforms and applications of the structure of my invention, throughoutwhich description reference is made to the accompanying drawings, inwhich:

Fig. 1 is an end or face view of a filter unit embodying the presentinvention, showing the air directing partitions in dotted lines and alsoshowing the stiffening members in dotted lines. Fig. 2v is an enlargeddetailed sectional View taken substantially as indicated by line 2 2 onFig. l. Fig. 3 is a sectional view taken as indicated by line 3 3onFig. 1. Fig. 4 is an enlarged transverse sectional view taken asindicated by line 4 4 on Fig; 3./ Fig. 5 is a view taken substantiallyas indicated by line 5 5 on'Fig. 4 with the' corrugations occurring inone of the screens ofv the filter pad indicated in dotted lines. Fig. 6is an enlarged view taken as indicated by line 6 6 on Fig; 5 being aview showing the manner in which the plain and corrugated screens aresuperimposed or arranged in the laminated con-V structionthat forms thefilter pad. Fig. 7 is a view showing a reinforcing or stiffening memberapart from the rest of the structure. Fig.V 8 is an en-` larged viewshowing the manner in which the edge portion of the screen is formed sothat it is not subject to fraying or distortion. Fig. 9 is an enlargeddetailed view taken as indicated by line4 9 9 on Fig. 2, being a viewshowing the manner in which each sheet of screen involved in the' filterpad grips the stiffening rod located in the pad. Fig. 10 is a viewsimilar to Fig. l, showing a'unitjof slightly different form andindicating a different arrangement of stiffening membersY in the pad.Figs. l1 and 12 are views illustrating the manner in which I carry outmy method of apiplying a stiffening rod to a metal filter pad. Fig'. 13.is an edge or side View of a modified form of unit wherein the frame ofthe unit instead of bei ing Aat or in a single fiat plane, is arcuate or3 curved, the view showing a pad in its initial form ready for insertioninto the arcuate frame. Fig. 14 is a sectional view taken as indicatedby line III-I4 on Fig. 13 and Fig. 15 is a view similar to Fig. 13except that the pad is in place, the stiffening rod of the pad beingshown curved to conform to the curvature or arcuate shape of the frame.Fig. 16 is a view taken at one corner of the frame showing the.construction that I provide for joining a side of the frame with the endwhich is separable from the side, and Figs. 17,. 18 and 19 are viewsillustrating the steps that I.

employ in assembling the structure to gain' a nished structure whereinthe detachable section of the frame is hooked in place andiszmaintained.in that position by the resiliency of the pad within the frame.

The structure that I will first describe beingthe form of the inventionillustrated in Figs.. 1 to..9.

inclusive, and 16 to 19, inclusive, involves, generally, a rigidholderor frame A, one or more filter pads B carried inthe frame, one or morepartitions- C serving to reinforce and stiien the structure to channel.air therethrough, and one or more stiieners D incorporated inthe filterpad or assembly of lter pads carried in the frame.

The frame A of my construction is amounting element or carrier for thepad or. pads that I em-v ploy, and in practice it may vary widely inform, shape and proportions. In the form of thev invention beingdescribedY I show a` frame that is polygonal in form and shape and whichis sectional in construction.` When the frame is square or rectangularin form it may have a main section X which is U-shaped, and it may havea simple straight end section Y which forms a closure` for the U-shapedmain section. Inl the particular frame illustrated the mainsection Xoftheframe has what may be termed an end portion I0. and parallel sideportions. I I projecting fromv the ends of the portion I0. 'The closurevsectionA Y of. the. z

frame is joined to and extends between the outer ends of the sideportions II and when in place the frame is complete. and forms aneiectiveholder or enclosure for the. lter pad. or pads, as

the case. may be.k In accordance with the pre-A trated involves lockingpins I8 inserted through the end portions of the side members II and thehook parts I5, as well as through the bars I6, as clearly illustrated inFig. 19 of the drawings.

In accordance with the broader principles of my invention I may employone or more filter pads or bodies in a frame such as the frame A. Thepad or pads B are such as to form a structure or assembly that occupiesthe frame A so that it is conned laterally between sides I2 of the frameparts and endwise or axially of the unit by the flanges I3. In Fig. 1 Iillustrate a unit wherein there are three separate or distinct fllterpads adjacent padsv being separated by partitions C, as will behereinafter described.

Each pad B is a. metal pad involving a multiplicity of metal parts soarranged and related as to form' a ready passage for air at the sametime forming tortuous channels or passages through which the air mustmove, to the end that partic1escarriedbythe air are deposited in thepad. I- preferably employ a metal pad formed entirelyof wire screeningor screens. A highly efficient, practical metal pad. of this. type isprovided by establishing a laminated structure or pad involvingalternately arranged. flat and corrugated sheetsof screening.. In thedrawings I illustrate flat sheets 20 of wire screening and corrugated.sheets 2'I of Wire screening., andas I have shown in the drawings, Iprefer to alternate the flat and corrugated. sheets. For mostsatisfactory results I do. not provide simple, straight corrugations` inthefcorrugated sheets 2l either axially of the unit or in any otherparticular direction, but ratherv I provide angular corrugations` suchas are indicated in dotted lines Fig. 5fso that the clear air passagesestablishedv by the corrugationsv do not extend straight through theypad from one sidev to the other, butestablish zig-zagA courses for theair to the end that no air finds its` way straight or directly throughtheY pad; but all air passing, through the pad isi deflected one way oranother.

from a truly axial course.

ferred form of my invention each frame. part, thatV is, each end partand eachside` partlcf the frame'` is channel-shaped incross-sectionalconfiguration and involves an outer wall -I2 and inwardly projectingside walls or anges I3 extending inward from. the sides or margins ofthe walls I2, as clearly shown in Fig. 3 of the drawings.

In the preferred form of my. invention the means provided for joining orsecuring the. endsA of the frame section Y tothe outer ends ofthe sidemembers II of. framesection X is preferably a hook means. The. form of`hook means illustrated in Figs. 16 to 19Y ofthe drawings involves atongue I5 projecting from the outer end of each.

side member II and turned inwardly and back' to form an inwardly facinghook, as clearly'shownv in Figs. 17, 18 and 19 of the drawings. Bars I6'are provided at the ends of the frame member Y to be engaged in thehooks formed by the parts. I5. The bars I6 may be. formed at. the. endsoi frame section Y byA providing inwardly turned flanges at the ends ofthis frame section and by providing openings or passages IT where thevanges join the frame section, which` openings,V serve to admit oraccommodate the hookV parts as will be apparent from the drawings. WhenVthe hook type fastening means is employed I' may provide a lock forpositively preventing release of the bars I6 from the hooks I5. In thepreferred form of the invention' the locking means When. employingy wirescreening in the formation of thelterpad and: for ordinary purposes',

that, is, for handling air,rv I preferl to. employ screening of. thetypev and weightordinaril'y em.- ployed as; windovrscreening.. Itzis.desirable, however,to employ/a. screenconstruction wherein the. meshesor-wresare not all uniform but rather have theoutermost strands or'edgewires 33 woven somewhatk closer togetherthan are. the other strands,thus. giving stability and rigidity to the edgesv of the` screens crsheetsv making it simple. to handle them in the'course of manufacture.

In accordance. with "my invention I provide thev wires.` of the sheets'of screening with a coating of a material which serves as a binder toretain the sheets in position' or against racking; Itf is. significantthatV I employ a; coating or binderl on the sheets of screening which issoftened by the application ofv heat sothat the stiieners whichV Iapply, in accordance with the method that I have provided, are'l bondedor bound tothe sheets off the pad by the binder initially applied to thesheets and serving at all times to holdl the sheetsv` against racking. Imay, in practice, use various materials as the coating or binder onthesheetsA of screening. As an example of a simple, practical' materialI will referv to common varnish, which may be applied to the sheets in avery thin.A film so that it is barely detectable.

' When Iy provide a partition or partitions C in theunit-Iiprefer thateach partition be formed ofv illusa single nat sheet of material such asmetal-,and

n practice I 'can employ thin sheet metal. In the form of the inventionbeing described I show three pads B n which case I employ two parttionsC as is clearly shown in Fig. 1 of the drawings. In the arrangementillustrated the pads C are in planes parallel with the axis of the unitand they extend between the sides I l of frame section X.

Ordinarily I find it unnecessary to employ any screening or sheets inthe structure other than the flat and corrugated screens 20 and 2|.However, I may, as I have shown in the drawings, employ an end sheet V35of screening at either or both ends of the unit. In the drawings, I haveshown a single end sheet 35 and I have shown the partitions C anchoredto the end sheet 35 by ties 4.0. The ties are U-shaped wires with outerparts 4j engaged over the outer side of the sheet 35 and having legs 42extending at opposite sides ofthe partition and provided at their endswith hooks 43 engaging around the partition. Through sucha constructionthe. partition is effectively joined to the sheet 35 and the sheet inturn is bound in the structure or is retained between the pads B andthe. frame, as clearly shown in Fig. 3 of the draw'- in s.

EIn accordance with my invention I provide the structure with one ormore stiifeners D. In the particular case being described I show twostiffeners D and I show them arranged in spaced relation and extendinglengthwise across the unit from one end to the other. Each stiffener Dis preferably a simple, straight wire or light rod incorporated entirelywithin or conned to the pad or assembly of pads that is, in turn,arranged in the frame.j It is important that the stilIener orstilenersgas the case may be, be confined entirely within the coniinesof the pad or assembly of pads, so that there are no ends or projectionsprotruding in a manner to in any way interfere with the frame or otherparts as the pads are being handled, or as they are being assembled intothe frames, in that projecting parts such as-the ends of members such asthe stileners materially impede assembly and are generally undesirable.

In accordance with my construction I employ a stiiiener D preferably alength of wire such as the length 4420i wire shown in Fig. '7, whichsomewhat larger in cross section than the openg-= ings or mesh of thescreening employed in thel sheets 20 and 2|. By thus providing a wire 44as a stiffener which is larger than the mesh of the screening, and byapplying the stiffener by the method that I will hereinafter describe,Iobtain a finishedestructure in which the stiffener passes through eachsheet of the pad, spreading wires of the sheet so that the stiener iseffectively gripped by the wires in two different directions, that is,in the direction indicated by the arrow a in Fig, 9, as well as in thedirection in-r dicated by the arrow b in Fig. 9. It is to be understoodhow the mesh or Woven construction of the sheets tends to maintainthewires of the sheets in parallelism and how insertion of the wire 44 to.a position such as is shown in Fig. 9, causes flexure of the wires ofthe sheet, leaving them in a condition so that they effectively bearagainst the Wire 44 and grip it. Furthermore the presence of the binderor coating that I provide on the sheets of screening resists spreadingof the wires of the sheet to admit the stiffener wire 44 and thus tendsto concentrate the spread of the wires of the sheet to the point wherethe stiffener wire v44 passes through the sheet. The particularstiffener wire 44 illustrated in the drawings is pro'- vided at one endwith a sharpened part or point 45 to facilitate its being operated inaccordance with the method that I have provided, whereas the other endof the wire 44 is preferably plain and simply cut oil, as shown in Fig.'7.

In the form of the invention illustrated in Fig. 10 of the drawings Ishow a frame A' which is substantially square rather than beingelongated as is the frame shown in Fig. 1. There'is a single pad B shownin Fig. 10 and this pad is free of or is without partitions C. The padB' is, however, provided with two stiieners D and these stiffeners,instead of being spaced and parallel and extending parallel with theside parts of the frame, as are the stiffeners in Fig. 1, are crossed orangularly related being arranged so that they extend between the cornersof the padB providing a crossed stiffening structure in the pad.

In the form of the invention illustrated in Figs. 13 to 15 the frame A2instead of being a flat rectangular frame is a rectangular frame that isarcuate or curved. When this form of the invention is fully assembled,as shown in Fig. 15, the stiffening member or members D2 extendlengthwise or in the direction of curvature. In fact, they follow thecontour or curvature of the frame A2 in spite of the fact that, asinitially formed, the pad has the members D2 in it so that they arestraight as they are in the pad shown in Fig. 1. In accordanceV with themethod that I Will hereinafter describe I am able to place the filterpad having one or more straight stiliening members D2 in the arcuateframe A2 so that in the nished form the stiffening member or members arearcuate like the frame, and I utilize the presence of the stiffeningmembers in the frame to maintain the pad against undesirable deection inthe course of its being arranged in place in the frame.

In accordance with the method that I have provided and which is thesubject of my divisional application entitled Method of Making Filters,led August 30, 1949, Serial No. 113 232, I form a iilter pad involvingan assembly of screens, preferably a laminated structure involvingalternate fiat and corrugated screens, by first holding the assembly ofscreens in the desired relationship, as shown in Fig. 11. I may, forexample, provide a carrier 50 that will properly accommodate the desiredlaminated assembly of screening.

The stiffener to be applied to or incorporated in the laminated metalassembly is mounted in a spinner S which may involve a chuck 60 to holdthe stiiener wire and a suitable motor 6l and drive 62 for operating thechuck at the desired speed. In Figs. 11 and 12 I illustrate anarrangement that may be used to advantage in which arrangement the chuck60 is arranged in a xed position, whereas the carrier 50 holding thelaminated assembly of wire screens is mounted on a movable carriage 10.The carriage shown has a guide 'H through which the stifener passesimmediately before entering the assembly of wire screening. With thespinner operating at a suitable speed, say. for instance, at about 2000R. P.

M. and the outer end of the guide wire guided in the guide 1|, thecarriage 10 is advanced toward the chuck 60 with the result that theouter pointed end 45 of the stiffener wire successively enters the meshof the sheets of screening spreading the wire thereof, as illustrated inFig. 9. When employing a wire stiifener 44 formed of a number l0 wire,and when turning the stiffener at about 2.000 R. P. M. a stiiener wireabout 36 inches sure to hold the hook connections tight.

long `can be readily advanced into a metal filter pad. The speed ofadvance may vary widely. However, I prefer to feed the carriage 'l0 asrapidly as possible without causing buckling or distortion of thespinning stiffener Wire 44.

The spinning wire with the pointed end is, in effect, drilled throughthe metal pad or it may be said to be spun through the metal pad, and inbeing inserted by a drilling or spinning action a substantial amount ofheat is generated and the heat thus generated serves to soften thebinder on the sheets of screening. When the stiffener wire is finallydrilled or spun into place the spinning or drilling operation is stoppedand the heat generated by the application of the stiffener is quicklydissipated so that the binder on the screening almost immediatelyadheres to the stiffener to act with the gripping effect of the wires ofthe several sheets of screening, to the end that the binder ispermanently, securely and dependably anchored in the filter pack.

In accordance with the structure that I provide the side members or endsof the frame A are provided with access openings or apertures I at thepoints where the stiffener wires 44 occur so that I may, if I desire,apply the stiffener wires to the pad or pads after the pad or pads havebeen assembled in the frame. In accordance with the broader principlesof my invention, however, I contemplate application of the stifenerwires to the assembly of wire screening either before or afterapplication of the pads to the frame. By having provided a structurewherein the stiifener wire or wires are entirely free of and are in noway connected to the frame, I am able to conveniently and efficientlyapply them either before or after application of the pads to the frame,and if they are to be applied after the pads have been applied to theframe it is merely necessary to provide the frame with the necessaryaccess openings 15.

Further, in accordance with the method that I have provided, Isimultaneously engage the hook connections between the frame sectionsand provide an assembly wherein the pad or pads are under compressionwith the pads exerting pres- My initial step is to arranged the pad orpads in the U-shaped main section of the frame and to apply the endsection of the frame to the outer or exposed end of the pad or. padassembly. I then spread the side members H of the frame section Xslightly apart or outward, as shown in Fig. 17, and follow the spreadingof the sides r of the frame section X with collapsing pressure on thepad or pads, which collapsing pressure is applied through the endsection Y toward the end Ii) of the main frame section X. When the pador pad assembly has been compressed to a position such as is shown inFig. 18 I return the sides Il of the main frame section X to theiroriginal and normal position, and in so doing I engage the hooks l5 overthe bars I6. I then release the compressing pressure from the pad or padassembly allowing the resilience of the metal structure of the pad toforce the end secl tion Y of the pad outwardly, as indicated by thearrows in Fig. 18, until the bars I6 are seated in the hooks I5, asshown in Fig. 19 of the drawings. I preferably proportion the pad or padassembly to the frame so that the pad continues to exert a pressureoutward on the end section Y of the frame, thus maintaining the severalsheets of the pad or pad assembly in tight seated engagement one withthe other. when lock pins n argenti] ployed they are inserted followingengagement of the bar I6 with the hooks I5. v

When employing the form of the`vvv invention illustrated in Figs. 13 tol5, inclusive, I prefer to apply the stiffening wire or wires to the padpreliminary to the pad being arranged in the arcuate frame. In that casemy i'lrst step is to arrange the flat stiffened pad at the open end ofthe U-shaped arcuate frame section and then apply pressure to the outeror upper end of the pad or pad assembly, as indicated by the arrow inFig. 13, forcing the pad down or through the curve of the frame untilthe pad is nally completely seated in the frame. In the course of thisapplication the initially flat pad, even though stiffened by thestiifening wire or wires, is curved or bent to conform to the arcuateformation of the l frame so that in the final assembly the entire pad isarcuate in form and the stiffening wires D2 incorporated therein arelikewise or correspondingly curved or arcuate. In the course of thisoperation it is highly advantageous to have the stiiening wiresincorporated in the laminated assembly of screening as they serve toprevent distortion or buckling of the pad as it is being forced into thearcuate frame.

In practice I have found it advantageous to apply the lter pads to theframes or to insert the filter pads in the frames and to join lthesections of the frames prior to application of the stiiiener orstiifeners, in which case the access openings in the frame parts arenecessary. Further, in carrying out my method I employ a stiffenerlongerthan necessary, while the drilling or .spinning-in operation is beingperformed, and

tion, penetrate the pad not only by spreading the wires of the screenswhich make up the pad, but also by penetrating sheet metal parts such.as partitions that may be present in the pad.

For example, I may initially form or assemble the pad by assembling theWire screens and the partitions and thereafter I apply or drill intoplace the stiffeners.

From the foregoing description it will be ap parent that I have, by mypresent invention, provided a filter unit which involves an exceedinglysimple frame, a significant feature of the frame f being the hookedconstruction by which the detachable section is secured to the mainsection. Further,- it will be apparent that I have provided a metal lterpad or a filter pad formed of metal screening which type of pad is suchas to effectively" resist the application of any ordinary reinforcingmeans. The stiffening wiresor rods that I vhave applied are confined tothe pad'or pad assembly and as above pointed out, are thereby entirelyfree of the frame and provide a simplied, practical construction havingthe features and advantages of effective reinforcement and stiffeningwithout the difculties and disadvantages inherent in structures wherereinforcing structures are dependent upon the frame for anchorage orsupport. Furthermore, it is significant to note that I have provided apad involving a stiflening wire extening therethrough and having thewires of the sheets of screening that form the pad bonded together andin gripping and bonded engagement with the stiffening Wire.

Having described only typical preferred forms and applications of myinvention, I do not wish to be limited or restricted to the specificdetails herein set forth, but wish to reserve to myself any variationsor modifications that may appear to those skilled in the art and fallWithin the scope of the following claims.

Having described my invention, I claim:

1. A filter unit including, a metal pad formed of a plurality of sheetsof Wire screen laid one over the other in a laminated mass, and a rigidrod in the mass passing through each of the sheets, the openings throughthe screens being smaller than the rod and one opening of each screenbeing enlarged by passage of the rod so the rod is grpped by the screen,and a frame holding the pad by its edges and under compression in adirection normal to the planes of the sheets.

2. A filter unit including, a metal pad formed of a plurality ofseparate sheets of metal screen forming a pack and a stiffening yrodengaged through each of the sheets, bonding connecting the rod andsheets holding the sheets in predetermined positions and againstmovement relative to each other, and a frame supporting the pad byengaging the edge portions of the pack of sheets.

3. A filter unit including, a pad formed of a plurality of separatesheets of metal wire screen coated with a binder and laid one overanother forming a pack, and a stiffening rod through the pack engagedthrough each sheet and bonded to each of the sheets by the coating onthe sheets, and a frame supporting the pad.

y4. A filter unit including, a pad formed of a plurality of separatesheets of metal wire screen coated With a binder and laid one overanother forming a pack, and a stiiening rod through the pack passingthrough each sheet and deflecting adjacent wires of each sheet so theybear on and grip the rod, the rod being bonded to each sheet by thecoating on said wires, and a frame supporting the pad.

5. A filter-including, a frame defining an opening, a substantially atpartition in the frame with its plane in the direction of the openingthrough the frame, packs at each sid-e of the partition each includingWire screens the planes of which are parallel with that of thepartition, and a stiiening rod extending through the packs of screensand through the partition, the rod being in engagement with each screen.

6. A filter pad including a sheet metal partition, a laminated pack ofWire screening at each side of the partition, and a stiffening rodextending through each screen of each pack and through the partition,the rod being in pressure engagement with the screens to be grippedthereby.v I

7. A filter including, a substantially rigid frame having separablesections and hook means joining the sections, and a iilter pad held inthe frame and including a plurality of superimposed layers of .wirescreen held tight together by the frame- 1 and acting to normally holdthe hook means i engaged; i:

8. A lter unit including, a metal pad formed ofza plurality of sheets ofwire screen laid one over the other in a laminated mass, and a rigid rodin the mass passing through each of the sheets, the. openings throughthe screens being smaller than the rod and one opening of each l()Yscreen being enlarged by passage of the rod so the rod is gripped by thescreen, and a frame holding the pad by its edges.

' 9. A lter unit including, a metal pad formed of a plurality of sheetsof Wire screen laid one pos'sed in the mass with its longitudinal axisnormal to the planes of the sheets of screen through Which the rod isengaged.

10. A lter unit including, a metal pad formed `of, a plurality of sheetsof Wire screen laidione over the other in a laminated mass, and a rigidi-rod in the mass passing through. each of the sheets, the openingsthrough the screens being smaller than the rod and one opening of eachscreen being enlarged by passage of the rod so the rod is gripped by thescreen, bonding connecting the rod and sheets holding the sheets inpredetermined positions and against movement relative to each other, anda frame holding the pad by its edges,v the rod being disposed in themass with its longitudinal axis normal to the planes of the sheets ofscreen through which the rod is engaged.

11. A lter unit including, a metal pad formed of. a plurality of sheetsof Wire screen laid one over the other in a laminated mass, a framesupporting the pad by its edges, and a rigid rod extending through thepad to pass through a plurality of the sheets and being inclinedrelative to the planes of the sheets to extend diagonally through themass and be slanted relative to each sheet, the size of the rod beingrelated to the size of openings through the screens so the screens aredeformed Where the rod is engaged therethrough and thus grip the rod.

l2. A lter unit including, a metal pad formed of a plurality of sheetsof wire screen laid one over the other in a laminated mass, a framesupporting the padv by its'edges, a rigid rod extending through the padto. pass through a plurality of the sheets and being inclined relativeto the planes of the sheets to extend diagonally through the mass and beslanted relative to each sheet, and bonding connecting the rod andsheets holding the sheets in predetermined positions and againstmovement relative to each other, the size of the rodbeing related to thesize of openings through the screens so the screens are deformed wherethe rod is engaged therethrough f and thus grip the rod.

13. A lter unit,including, a substantially rectangular metal pad formed'cfa plurality of sheets of wire screen laid one over the other in alaminated mass, a frame supporting the pad by its edges, and a stiieningrod extending diagonally through the pad between opposite cornersthereof to be slanted through each of the she ,fthe size of the rodbeing related to 'f openings through the screens so the screens aredeformed where the rod is engaged therethrough and thus grip the rod.

14. A lter unit including, a substantially rectangular metal pad formedof a plurality of sheets of wire', lscreen laid one over the other in alaminated mass, a frame supporting the pad by its" edges, a stiieningrod extending diagonally through the pad between opposite corners.,vthereof to be slanted through each of the sheets, 'and bondingconnecting the rod and each of the sheets holding the sheets inpredetermined positions and against movement relative to each other, thesize of the rod being related to the size of openings through thescreens so the screens are deformed where the rod is engagedtherethrough and thus grip the rod.

15. A filter unit including, a rigid rectangular frame formed ofconnected members with spaced flanges defining inwardly faced channels,and a at rectangular pad carried in the frame and having edge portionsand corner portions held in said channels, the pad including, aplurality of open mesh alternately plain and corrugated wire screenslaid one against another and in planes normal to that of the pad, and astraight rigid rod embedded in the mass and extending through thescreens and into opposite corner portions of the pad, the size of therod being related to the mesh of the screens so each screen is spreadWhere the rod extends therethrough.

16. A lter unit including a pad formed of a plurality of sheets of wirescreen laid one over the other in a laminated mass, a frame supportingthe pad by its edges, and a plurality of stiffening rods extendingthrough the pad in different directions relative to each other and witheach rod extending through a plurality of the sheets, the size of therods being related to the openings through the sheets so each sheet isdeformed Where a rod extends therethrough and thereby grips the rod, therodsbeing inclined to the planes of the sheets so each rod is slantedthrough each sheet engaged thereby.

17. A filter unit including a pad formed of a plurality of sheets ofwire screen laid one over the other in a laminated mass, a framesupporting the pad by its edges, a plurality of stiffening rodsextending through the pad in different directions relative to each otherand with each rod extending through a plurality of the sheets, andbonding connecting the rods and the sheets engaged thereby holding thesheets in predetermined positions and against movement relative to eachother, the size of the rods being related to the openings through thesheets so each sheet is deformed where a rod extends therethrough andthereby grips the rod, the rods being inclined to the planes of thesheets so each rod is slanted through each sheet engaged thereby.

18. A filter unit including a pad formed of a plurality of sheets ofwire screen laid one over the other in a laminated mass, aframesupporting the pad by its edges, and a plurality of stiffening rodsextending through the pad, each rod being engaged through each sheet ofthe mass, the size of the rods being related to the openings through thesheets so each sheet is deformed where a rod extends therethrough andthereby grips the rod, the rods being pitched to extend in differentdirections relative to each other and to be inclined to the planes ofthe sheets so each rod is slanted through each sheet.

`19. A filter unit including a pad formed of a plurality of sheets ofwire screen laid one over the other in a laminated mass, a framesupporting the pad by its edges, a plurality of stiffening rodsextending through the pad, each rod being engaged through each sheet ofthe mass, and bonding connecting each rod and each sheet thereby holdingthe sheets in predetermined openings through the sheets so each sheetisV deformed where a rod extends therethrough andthereby grips the rod,the rods being pitched to extend in different directions relative toeach other and to be inclined to the planes of the sheets so each rod isslanted through each sheet.

20. A filter unit including a pad formed of av plurality of sheets ofwire screen laid one overv the other in a laminated mass, a rectangularvframe so each sheet is deformed where a rod ex tends therethrough andthereby grips the rod.

21. A filter unit including a, pad formed of aplurality of sheets ofwire' screen laid one over the other in a laminated mass, a rectangulari frame supporting the pad by its edges, a plurality of stiffening rodsextending through the pad in different directions to cross one anotherand with each'rod slanted through a plurality of the sheets and betweenopposite corners of the frame so each sheet is deformed where a rodextends therethrough and thereby grips the rod, and bonding connectingeach rod and each sheet thereby holding the sheets in predeterminedpositions and against movement relato to each other.

22. A filter unit including, a pad formed of a plurality of sheets ofwire screen laid one over the other in a laminated mass, a framesupporting the pad from its edges, and a plurality of straightstiffening rods extending in different directions through the pad andinclined to the planes of the sheets, each rod being slanted.

through a plurality of the sheets, the size of the rods being related tothe openings through the sheets so each sheet is deformed where arodstiifening rods extending in different directions through the pad andinclined to the planes of the sheets, each rod being slanted through aplurality of the sheets, the size of the rods being related to theopenings through the sheets so each sheet is deformed where a rodextends therethrough and thereby grips the rod, and bonding connectingeach rod and the sheets engaged thereby so the sheets are held inpredetermined positions and against movement relative to each other, therods being completely embedded in the mass and crossing each other atthe middle of' the mass.

24. A filter unit including, a rigid rectangular frame formed ofconnected members with spaced flanges defining inwardly faced channels,a flat rectangular pad carried by the frame and having edge portions andcornel` portions held in said channels, the pad including, a pluralityof open mesh alternately plain and corrugated screens laid one againstanother and in planes normal to that of the pad, and a plurality ofstraight,

screens, each rod being slanted through eachr screen and the size oftherods being related to the openings through the screens so each screen isdeformed where va rod extends therethrough I3 and thereby grips the rod,the .rods being crossed at the middle of the pad with each rod extendingbetween opposite corner portions of the pad.

RICHARD S. FARR.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,113,430 Greenwalt Oct. 13, 19141,143,655 Sommers June 22, 1915 Number

